Dynamics of the perinuclear theca

Abstract

The perinuclear theca contains many molecules such as MN13 (Manandhar and Toshimori 2003; Toshimori et al. 1991), PERF15 (Oko and Morales 1994), multiple-binding proteins (capping proteins α3 and β3) (von Bülow et al. 1997), actin-related protein (Arp)-T1 and Arp-T2 (Heid et al. 2002), the calmodulin-binding peptide (CaMBP) (Lécuyer et al. 2000), calicin (expressed in the postacrosomal calyx) (Leclerc and Goupil 2000), phospholipase C (PLC) zeta (Saunders et al. 2002; Yoda et al. 2004), SubH2B (Aul and Oko 2002), cysteine-rich PT1 (CYPT1) (Hansen et al. 2006), and postacrosomal sheath WW domain-binding protein (PAWP) (Wu et al. 2007). Ultrastructural observations reveal that electron-dense materials gradually accumulate in the nascent PAR of elongating spermatids as precursor substances for the biogenesis of the perinuclear theca (Bellvé et al. 1992; Kann et al. 1991; Longo and Cook 1991). This accumulation occurs actively in late elongating spermatids and gradually results in the formation of the paracrystalline sheet or the PAS.

Interestingly, the cytoskeletal components of the paracrystalline sheet and PAS are not formed either in the round-headed spermatozoa produced by GOPC− ^/− mutant mice (Ito et al. 2004) or in the spermatozoa produced by humans with globozoospermia (Escalier 1990). These lines of evidence suggest that substances in the perinuclear theca regulate the shaping of the sperm head by keeping the developing nucleus bound to the acrosome and plasma membrane. Similar findings have been reported previously (Oko and Maravei 1995; Oko and Morales 1994).